How to Set Your Google+ Cover Photo Size
Choosing the best size for your cover photo has gotten more complicated now that Google+ has cut the available space at the top of each profile page by splitting the cover area into two parts:
Right side: This section — two thirds of the design — holds the image you upload.
Left side: This smaller section (one-third) holds the profile photo and text.
Behind the text and profile photo in the left third, Google+ automatically generates a copy of your cover image with very a strong blur effect. To take best advantage of the space, you want to upload an image that looks good in just two thirds of the cover area, and that will look good when blurred behind your profile image, as well.
To take best advantage of the limited options on Google+, keep these image parameters in mind when you design your profile and cover images:
Google+ uses the responsive design approach to adjust the size of images to best fit the display of large and small screens.
The maximum size of the cover area is 2120 x 1192 px.
The minimum size of the cover area is 480 x 270 px.
In general, use images that are a little larger than Google recommends because you’re given the option to crop, as you upload it. That way, cutting a little off the image is relatively easy as you position and crop the image to best fit the space.
Consult the latest notifications for the latest on Google changes.